The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Generally, some of heat generated at a combustion chamber of an engine is absorbed by a cylinder head, a cylinder block, intake and exhaust valves, and a piston, etc.
When temperatures of the constituent components of the engine excessively increase, the constituent components may be thermally deformed, or an oil film of an inner wall of a cylinder may be damaged such that lubrication performance deteriorates, resulting in thermal problems of the engine.
Due to the thermal problems of the engine, abnormal combustion such as combustion failure, knocking, etc. occurs, thus a piston may be melted, which may result in serious damage to the engine. Further, thermal efficiency and power of the engine may deteriorate. In contrast, excessive cooling of the engine may cause the power and fuel consumption to deteriorate, and may cause low temperature abrasion of the cylinder, thus it is desired to appropriately control temperature of the coolant.
In this respect, in a typical engine, a water jacket is provided inside a cylinder block and a cylinder head, and a coolant circulating in the water jacket cools a periphery of a combustion chamber and metal surfaces such as peripheries of an exhaust port, a valve seat, etc.
The water pump is connected with auxiliary components of the engine through the belt, and is continuously driven with the starting of the engine to circulate the coolant to the cylinder block and an exhaust gas recirculation (EGR) cooler regardless of warm up condition or cooling condition of the engine.
In addition, the engine according to the related art stops the flow of the coolant passing through the cylinder block to improve the warm-up speed of the engine.
However, the flow of the coolant passing through the cylinder block is only stopped, but the coolant passing through the cylinder head is continuously circulated.
That is, the fuel efficiency and the exhaust gas are stabilized when the engine is warmed up, but since the coolant continuously circulated to the water jacket formed in the cylinder head in a condition that the engine is cold, the warming period of the engine becomes longer, and fuel efficiency is low and the exhaust gas quality is deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.